Development of Thick-foil and Fine-pitch GEMs with a Laser Etching Technique

Abstract We have produced thick-foil and fine-pitch gas electron multipliers (GEMs) using a laser etching technique. To improve production yield we have employed a new material, liquid crystal polymer, instead of polyimide as an insulator layer. The effective gain of the thick-foil GEM with a hole pitch of 140 μ m , a hole diameter of 70 μ m , and a thickness of 100 μ m reached a value of 10 4 at an applied voltage of 720 V. The measured effective gain of the thick-foil and fine-pitch GEM ( 80 μ m pitch, 40 μ m diameter, and 100 μ m thick) was similar to that of the thick-foil GEM. The gain stability was measured for the thick-foil and fine-pitch GEM, showing no significant increase or decrease as a function of elapsed time from applying the high voltage. The gain stability over 3 h of operation was about 0.5%. Gain mapping across the GEM showed a good uniformity with a standard deviation of about 4%. The distribution of hole diameters across the GEM was homogeneous with a standard deviation of about 3%. There was no clear correlation between the gain and hole diameter maps.